Yoshimura Y, Okamoto T, Tamura T
Faculty of Applied Biological Science, Hiroshima University, Japan.
J Reprod Fertil. 1993 Jan;97(1):189-96. doi: 10.1530/jrf.0.0970189.
This study examined structural changes in oocyte and follicular wall during oocyte maturation in Japanese quails. The structures of the germinal disc and the surrounding follicular wall were observed by light and electron microscopy 25, 6 and 1 h before the expected time of ovulation. The germinal disc of the oocyte was located near the oocyte plasma membrane at 25 h before ovulation, and the germinal vesicle was located in the centre of the germinal disc. Numerous cytoplasmic elements, such as elongated membrane-bound vesicles, mitochondria and glycogen granules were also observed in the germinal disc. The surface of the oocyte made close contact with the cytoplasmic processes of the granulosa cells. Six hours before ovulation, fluid filled spaces formed between the oocyte and follicular wall. At 6 h before ovulation, the germinal disc was similar to that at 25 h before ovulation, whereas the oocyte and the granulosa cells were disconnected. Myelin bodies and dense bodies developed in the cytoplasmic processes of the granulosa cells, suggesting that lysosomal enzymes were activated. In the follicle at 1 h before ovulation, the second maturation spindle was located just beneath the surface of the oocyte, and the first polar body was in the perivitelline space. In the germinal disc, the membrane-bound vesicles were swollen and well developed. We suggest that, during the process of early oocyte maturation, the junctions between the oocyte and granulosa cells are disconnected, and factors that promote oocyte maturation may be activated in the germinal disc since the membrane-bound vesicles are developed.
本研究检测了日本鹌鹑卵母细胞成熟过程中卵母细胞和卵泡壁的结构变化。在预计排卵时间前25小时、6小时和1小时，通过光学显微镜和电子显微镜观察生发盘及周围卵泡壁的结构。排卵前25小时，卵母细胞的生发盘位于卵母细胞质膜附近，生发泡位于生发盘中央。在生发盘中还观察到许多细胞质成分，如细长的膜结合囊泡、线粒体和糖原颗粒。卵母细胞表面与颗粒细胞的细胞质突起紧密接触。排卵前6小时，卵母细胞与卵泡壁之间形成充满液体的间隙。排卵前6小时，生发盘与排卵前25小时相似，而卵母细胞与颗粒细胞分离。颗粒细胞的细胞质突起中出现髓鞘小体和致密小体，提示溶酶体酶被激活。在排卵前1小时的卵泡中，第二成熟纺锤体位于卵母细胞表面下方，第一极体位于卵周间隙。在生发盘中，膜结合囊泡肿胀且发育良好。我们认为，在卵母细胞早期成熟过程中，卵母细胞与颗粒细胞之间的连接断开，由于膜结合囊泡发育，促进卵母细胞成熟的因子可能在生发盘中被激活。
